Urothelium is a 3-4 layered cellular structure that lines the urinary space (renal pelvis, ureter, bladder and urethra). Abnormality in this epithelium can lead to a number of urogenital diseases including bladder cancer that accounts for about 5% of all cancer deaths. To control and eventually to prevent some of these abnormalities, we need to understand the biochemistry of urothelial differentiation, which is the long-term goal of this project. During the current grant period, we will conduct two series of experiments. In the first, we will grow cow urothelial cells in culture, and use them as a model for studying an "altered" state of urothelial differentiation. In another series of experiments, we will characterize a panel of urothelial differentiation antigens, with an emphasis on the so-called "asymmetric unit membrane (AUM)" which is a bladder-specific structure believed to play an essential role in maintaining the "stretchability" of normal urothelium. To identify the AUM subunits, we will use four approaches which are based on different but complementary principles. They are monoclonal antibody production, iodination of urothelial surface molecules, identification of cytoskeletal binding proteins, and two- dimensional gel analysis. Immunological and nucleic acid probes for these urothelial markers will be generated and used to study the structure and function of these molecules.